I never like wearing the mask owing to the increase in deadspace (=>rebreathing CO2) plus the possibility of inhaling whatever was left in there last time. I can't rule out other common causes for diarrhoea (however conincidental) I just can't think of what it was.

If the filters were not fresh, and the mask not clean, it's possible that it had undesirable stuff growing. Do you use the mask for other things? How much use does it get? How is it stored?

As for mixing Xtol, it's never been a problem for me, but that doesn't mean anything for your experience. I occasionally wear a nuisance dust mask when mixing, but usually forget.
Like Sal, I only heat the water to the minimum specified in the directions.

I may not be the most experienced dark room worker here, but I sure haven't seen anyone mixing a developer outside the dark room so far, and we don't even have a respirator. The fact that PeterB takes quite strong and uncommon precautions (mixes chems outside or with a respirator) indicates to me that he may be overly sensitive to some compounds. As has been mentioned already, some few people react strongly to chemicals that are used by many others without any issues.

So let's assume for a second that PeterB indeed developed a high sensitivity to SO2: in this case he should avoid ALL powdered developers, the all contain Sulfite in large doses. Gas masks won't block SO2, so unless he can mix in some outside area or a proper fume hood, liquid developers it is from today on. If you like the properties of Ascorbate developers but really have to avoid Sulfite, there is PC-TEA and PC-Glycol.

Not impossible but the timing was uncanny. I had nothing unusual or suspicious to eat that day and none of my other 4 family members had diarrhoea.

huh

that is weird ...

people get sensitive to stuff all the time.
sorry to hear that a developer you love is giving you the huckleberry 2step.

if it doesn't bother you mixing it in a better ventilated area you might just mix it there
but then again, it might affect/bother you when you process your film too ...
then there seem to be only a few choices ... a full hazmat body suit, don't use the developer ( use something else )
or start wearing diapers

i hope for the sake of your film, and sanity, it was something you ate, and not the developer
it stinks having to change everything you are used to ...

Leaving aside whether a particle-mask is a wise idea because of pre-existing known allergies (which you would already have known about), why would you have a dust cloud? Place the slightly opened packet a few millimetres above the water and shake-and-pour gently -- throwing the powders into the mixing container, in handfuls, from the other side of the room (possible slight exaggeration) is not a sensible way to proceed, even if you were only making a cake. Ingestion of the Xtol sounds as though it is unlikely to have caused your symptoms. In best practice, your protective equipment should be completely clean and sterilised before each use - this could well be a source of some fungal trigger for your illness.

As a chemist let me say that Xtol is probably the most benign of the commercially available developers. There is no free sulgurous acid in the mixed solution as noted in the MSDS. Your symptom is not associated with any of the chemicals in the developer. While I usually advocate taking safety precautions with darkroom chemicals. you fear of Xtol is unfounded and the respirator ineffectual. This is predicated on the assumption that you have never experienced an asthma like reaction before when exposed to sulfites say from drinking wine. In which case you would have tp give up darkroom work. I fear that you may be making too much out of something which probably has no relation to the Xtol. Like Scrooge you may have been suffering from an "undigested bit of beef."

Gerald said it best. I mix powders outside with a slight breeze at my back. The cut package is nearly submerged when adding to water. I can't imagine XTOL being the cause.

...I had the solution heated to about 31degC and could feel the fumes slightly acrid in my eyes as I didn't have sealing goggles on...

Originally Posted by Sal Santamaura

I'll let those with more expertise continue to discuss the possibility that there's any connection between XTOL and your symptoms, but wonder why you'd mix it at 31 degrees C? I've had no trouble getting Part A into solution at the low end of its instructions' temperature range, i.e. not much above 18 degrees C.

Originally Posted by bdial

...Like Sal, I only heat the water to the minimum specified in the directions.

Peter, again, why 31 degrees C?

It's been a loooong time since freshman chemistry. Chemists: wouldn't whatever might be the cause of Peter's problem be produced in greater quantity if the mixing is done at a higher than necessary temperature?